Clarification for non-Danes: this post is not entirely accurate. Not all Master's courses in Denmark have oral examinations, and many courses before the Master's level (including elementary school) have oral exams. It is unrelated to the academic level, and instead related to the academic discipline and the size of the course. The latter is in my experience the main constraint, as oral exams are difficult to scale. They usually take 20-30 minutes per student, and if you have a course with 200 students, well, you're in for a long time.

The oral exam format described is also somewhat unusual, in my experience. It is usually the case that there is one internal examiner and one external examiner in the room. More than that would be ruinously expensive. The format varies; usually it's a combination of a short presentation and questions asked by the examiner. Drawing a random topic is very common.

Source: I am a university teacher in Denmark who teaches master-level courses without oral exams, and I have been an examiner for many oral exams at university level.